Muslims around the world began the month of Ramadan last Thursday, abstaining from food and drink during daylight hours.
The Islamic lunar calendar means that the start date of Ramadan moves forward by under two weeks every year versus the Gregorian calendar. In countries near or on the equator, such as Saudi Arabia, Singapore and Indonesia, this movement makes little difference to the hours of daylight critical to observe the fast.
But for those observing in the world's most northern countries near the Arctic Circle, the issue is more pressing in summer months.
In Iceland, the sun sets at midnight and returns two hours later during peak summer.
Icelandic Muslims can expect to fast for up to 21 hours and 51 minutes this year, with the sun setting at 11:57 p.m. on the final night of Ramadan on June 14.
Muslims living in countries where the sun doesn't set — or where the sun only drops momentarily — can follow one of three solutions offered by some Islamic scholars and organizations.
They can break their fast using the time of either the sunset in the nearest country that does not have near continuous daylight, the nearest Muslim-majority country, or observe Saudi Arabia's time. Otherwise, they can stick to observing local times.
Karim Askari, executive director of the Islamic Foundation of Iceland, is in no doubt which edict he will be following this Ramadan.
"I'll be going by the local time in Reykjavik," Askari told CNBC. "Going 21 hours without eating is a long time. But God willing, the majority of Muslims here in Reykjavik are doing it too."
Two mosques in Iceland's capital city have agreed to follow local dawn and dusk times to decide when they should break their fast. Other mosques and organizations have chosen to follow the times of other European countries. Askari said that one mosque in Reykjavik is following the times of a city in France.
"They can choose what they want. We have space in our community relations here," Askari said. "Some people cannot accept that they'll be eating when the sun is up, even if it's near midnight, because they are used to waiting in their home country — so they will go by local time. Others can accept that they'll have to eat even when the sun is partially up."